I don't think you need for a fortress with walls and whatnot. You want your End house to be functional and well-protected.
Personally, I just went with this approach:
-Made a moat around an area and filled it with water. <- So the Endermen can't get near
-Built a house in the middle, 2 spaces high. <-So the Endermen can't get in
-Covered the top with cacti. <-So the Endermen can't get above
-Avoided building another floor. <-So the Endermen can't get below
And that was it. I added an unprotected farm outside and some trees, and glass to see the surrounding area without provoking them. I sometimes stare at them and run in, and hear them crashing against my defenses helplessly. Of course, everything is well lit.